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BLAST EFFECTS AND RELATED THREATS

T. Krauthammer1

ABSTRACT

This paper contains a brief summary of blast effects and related threats, and provides anoverview of how these effects are related to force protection and homeland defense. Alsoprovided are conclusions and recommendations on addressing these urgent and vital needs.

Introduction

The purpose of R&D for the development of protective measures against explosions is toimprove existing capabilities and to create methods and products that could perform efficientlyunder anticipated threats. Furthermore, one should not only consider the physical environmentthat could be associated with explosive incidents but also an overall hostile environment whichmay include a large number of parameters. Also, the definition of failure is related closely tooperational concepts, mission and serviceability of a facility. Therefore, such parameters shouldbe considered during the planning of the required R&D. Other factors which may, and usuallydo, affect the defensive performance of a facility are related to psychological aspects of humanbehavior, and they should be considered in the overall process of system assessment.Nevertheless, the main thrust of this paper is aimed at a review of explosive effects and relatedthreats in support of developing realistic engineering recommendations for guiding futureassessment, design and research activities in the field of protective construction, based onavailable data. Furthermore, in order to simplify and narrow the scope of this paper it wasdecided to concentrate on the parameters which an architect and/or engineer would need for thedesign and/or retrofit a structural system. One needs to have specific information on the loadingenvironment in which the structure is expected to perform (e.g., load-time histories, radiationlevels, temperature-time histories, chemical/bacteriological (CB) conditions, etc). Naturally, suchenvironments can be defined only if an analysis of the threat or hazard is available. Then, onemust put these in the context of known and/or anticipated threats. Here, because of thesymposium’s theme, the focus will be more on terrorist attack than on traditional militaryoperations.

Since 1983, the United States has been subjected to international terrorism on a grand scale whenpowerful explosive devices were used against the US Embassy and the Marine Corps Barracks inLebanon. US government and military personnel deployed overseas and various other USorganizations became the target of international terrorists, desiring the United States to abandonits vital strategic interests in the Middle East. Besides the attacks against US facilities in the early

1 Prof. of Civil Engineering, Dir. Protective Technology Center, Penn State University,University Park, PA 16802, USA

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1980s, in November 1995, a car bomb exploded in Riyadh, Saudi Arabia, killing five Americanswho were working in the of offices of the Saudi Arabian National Guard. A few months later, inJune 1996, terrorists detonated the largest known truck bomb (more than 20,000 lbs of highexplosives) near Dhahran, Saudi Arabia. The explosion killed 19 US service personnel living in ahigh-rise apartment building at the Khobar Towers military complex. Hundreds more wereinjured. These incidents were followed by explosive attacks in August 1998 against USembassies in Kenya and Tanzania, and, in October 2000, against USS Cole in Yemen. Althoughthe previous terrorist attacks were directed against US land-based facilities, the USS Coleincident highlights the fact that US Navy ships and other sea-based facilities are a target forterrorist attack.

Prior to 1993, the United States had been relatively unaffected by terrorism within its borders.Then, in February1993, the US was attacked by externally-supported terrorist who targeted theWord Trade Center, and in April 1995, America was shocked by the devastating attack by home-grown terrorists against the Alfred P. Murrah Federal Building in Oklahoma City. These attacksbrought terrorism home to the US. The horrific terrorist attacks against the World Trade Centerand the Pentagon in September 2001 changed forever the way various federal, state and localgovernment agencies, and many other organizations would look at security and protection ofoccupants of their buildings.

In today’s environment, despite the end of the Cold War, the needs to protect both militaryfacilities and civilian populations from enemy attack have not diminished. This rapidly evolvingchange in threats is expected to continue well into the 21st Century. Furthermore, we noted anincreasing need to protect civilian populations against terrorism and social/subversive unrest.This situation is true for many parts of the world, and it may exceed the previous reasons for thedevelopment of protective technologies (i.e., related to military-sponsored work onfortifications). Unlike the global politically and ideologically motivated conflicts of the past,dominated by well-organized military powers, most of the armed conflicts in the last few yearshave been localized and dominated by social, religious and/or ethnic causes. This means thatwell-understood and reasonably-predictable military operations are replaced by much lessunderstood and less predictable terrorist activities. Such activities are carried out by determinedindividuals or small groups that have a wide range of backgrounds and capabilities. They aredirected against well-selected targets, and they are aimed at inflicting considerable economicdamage and loss of lives. As demonstrated by recent tragic incidents in the US, the term lowintensity conflict is a misnomer. Such activities, despite involving a few individuals or smallgroups, have devastating consequences. They can adversely affect national and internationalstability.

Defending society against terrorism requires a well planned layered approach, combininginnovative intelligence and law enforcement capabilities and effective protective technologies.The future of R&D in protective technology must be reshaped accordingly. Careful attentionmust be devoted to facilities whose failure could severely disrupt the social and economicinfrastructure of nations. One must employ innovative approaches that combine theoretical,numerical and experimental approaches, and to conduct these activities in a well-coordinatedcollaborative activity between government, academic, and private organizations. Although this

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paper reviews the state of the practice in blast effects and related threats, it will not address indetail many other important threats that must be considered for effective force protectionactivities. Many of these issues are addressed in several publications on this subject (e.g.,Conrath et al. 1999, ASCE 1985, Department of the Army 1986 and 1990, etc.).

Blast Effects

Blast effects are associated with either nuclear or conventional explosive devices. Althoughsmall nuclear devices (e.g., tactical size) could be used by terrorists, the corresponding effectswill not be addressed here. The interested reader can find useful information in other sources(e.g., ASCE 1885). Scaling laws are used to predict the properties of blast waves from large-scale explosions based on tests on a much smaller scale (Johansson and Persson 1970, Baker1973, Baker et al. 1983). The most common form of blast scaling is Hopkinson-Cranz or cube-root scaling (Hopkinson 1915, Cranz 1926). It states that self-similar blast waves are produced atidentical scaled distances when two explosive charges of similar geometry and of the sameexplosive, but of different sizes, are detonated in the same atmosphere. It is customary to use as ascaled distance a dimensional parameter, Z, as follows:

Z = R/E1/3, or Z = R/W1/3 (1)

where R is the distance from the center of the explosive source, E is the total heat of detonationof the explosive, and W is the total weight of a standard explosive such as TNT. Blast data at adistance R from the center of an explosive source of characteristic dimension d will be subjectedto a blast wave with amplitude of P, duration td, and a characteristic time history. The integral ofthe pressure-time history is the impulse i. The Hopkinson-Cranz scaling law then states that suchdata at a distance ZR from the center of a similar explosive source of characteristic dimensionZd detonated in the same atmosphere will define a blast wave of similar form with amplitude P,duration Ztd and impulse Zi. All characteristic times are scaled by the same factor as the lengthscale factor Z. In Hopkinson-Cranz scaling, pressures, temperatures, densities, and velocities areunchanged at homologous times. The Hopkinson-Cranz scaling law has been thoroughly verifiedby many experiments conducted over a large range of explosive charge energies. Limitedreflected impulse measurements (Huffington and Ewing 1985) showed that Hopkinson-Cranzscaling may become inapplicable for Z < 0.4 ft/lb1/3 (0.16 m/kg1/3).

The character of the blast waves from condensed high explosives is remarkably similar to thoseof TNT, and these curves can be used for other explosives by calculating an equivalent chargeweight of the explosive required to produce the same effect as a spherical TNT explosive. Ingeneral, the equivalent weight factors found by comparing airblast data from different highexplosives vary little with scaled distance, and also vary little dependent on whether peakoverpressure or side-on impulse is used for the comparisons. When actual comparative blastdata exist, these data can be used to determine a single number for TNT equivalence byaveraging. When no such data exist, comparative values of heats of detonation H for TNT andthe explosive in question can be used to predict TNT equivalence (US Department of the Army,Navy and Air Force 1990, U.S. Department of Energy 1992, Conrath et al. 1999).

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The theoretical heats of detonation for many of the more commonly used explosives are listed invarious sources (e.g., Appendix A of U.S. Department of Energy 1992), along with TNTequivalency factors. This method of computing TNT equivalency is related primarily to theshock wave effects of open-air detonations, either free-air or ground bursts, as shown in Table 1.Limitations of this approach have been discussed in such publications (e.g.., Conrath et al. 1999).Typical sources of compiled data for airblast waves from high explosives are for spherical TNTexplosive charges detonated under standard sea level. The data are scaled according to theHopkinson-Cranz (or cube-root) law. An acceptable set of standard airblast curves for thepositive-phase blast parameters is shown in Figures 1 and 2 (Kingery and Bulmash 1984,Department of the Army 1986, US Departments of the Army, Navy and Air Force 1990). Theprocedures in TM 5-855-1(Department of the Army 1986) have been implemented in thecomputer code ConWep (Hyde 1993) that can be used for calculating a wide range of weaponand explosive effects.

Unconfined Explosions

The blast curves in Figures 1 and 2 define the various scaled blast parameters as a function of thescaled distance Z = R/W1/3 up to a value of 100 ft/lb1/3 (39.7 m/kg1/3) . For most protectivestructures or even light structures, damage is relatively superficial beyond this scaled distance.The use of the charge weight W refers to TNT-equivalent weights. Figure 1presents the scaledform of the following parameters: Peak side-on overpressure, Ps (psi), side-on specific impulse, is(psi-ms), Shock arrival time, ta (ms), Positive phase duration, td (ms), peak normally reflectedoverpressure, Pr (psi), normally reflected specific impulse, ir (psi-ms), shock front velocity, U(ft/ms), wave length of positive phase, LW (ft). The normally reflected pressure and impulse aregreater than the corresponding side-on values because of the pressure enhancement caused byarresting flow behind the reflected shock wave. Various sources (e.g., U.S. Department ofEnergy 1992) present methodologies for calculating such parameters. Normally reflected blastwave properties usually provide upper limits to blast loads on structures, but one may have toconsider cases blast waves that also strike at oblique angles. The effects of the angle ofincidence versus the peak reflected pressure Prα and the reflected impulse irα are shown in Figures3 and 4. In these figures the angle α is 0Ε for a head on (i.e., normal) incidence and 90Ε whenthe wave travels parallel to the wall.

For an explosive charge detonated on the surface of the ground, one can use the free-air curves todetermine blast wave parameters by adjusting the charge weight in the ground burst to accountfor the enhancement from the ground reflection. For a perfect reflecting surface, the explosiveweight is simply doubled. When significant cratering takes place, a reflection factor of 1.8 ismore realistic. This simple approach is recommended for an explosion at or very near theground surface. This approach is still valid. However, a large volume of test data are availableand have been compiled from tests using hemispherical TNT charges on the ground surface.From these data, blast curves for the positive-phase blast parameters were developed and arewidely used as the standard for ground bursts. Consequently, these curves (U.S. Departments ofthe Army, Navy, and Air Force 1990) are presented here as Figure 4. Structures subjected to theexplosive output of a surface burst will usually be located in the pressure range where the planewave concept can be applied. Therefore, for a surface burst, the blast loads acting on structure

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surface are calculated as described for an air burst except that the incident pressures and otherpositive-phase parameters of the free-field shock environment are obtained from Figure 4.

Table 1. Averaged free-air equivalent weights (Conrath et al. 1999).

Explosive EquivalentWeight,Pressure(lbm 1)

EquivalentWeight,Impulse(lbm 1)

PressureRange(psi 2)

ANFO 0.82 - 1-100

Composition A-3 1.09 1.076 5-50

Composition B 1.111.20

0.981.3

5-50100-1,000

Composition C-4 1.37 1.19 10-100

Cyclotol (70/30) 1.14 1.09 5-50

HBX-1 1.17 1.16 5-20

HBX-3 1.14 0.97 5-25

H-6 1.38 1.15 5-100

Minol II 1.20 1.11 3-20

Octol (70/30, 75/25) 1.06 - -

PBX - 9404 1.131.7

-1.2

5-30100-1,000

PBX - 9010 1.29 - 5-30

PETN 1.27 - 5-100

Pentolite 1.421.381.50

1.001.141.00

5-1005-600

100-1,000

Picratol 0.90 0.93 -

Tetryl 1.07 - 3-20

Tetrytol (Tetryl/TNT) (75/25, 70/30,65/35) 1.06 - -

TNETB 1.36 1.10 5-100

TNT 1.00 1.00 Standard

TRITONAL 1.07 0.96 5-1001 To convert pounds (mass) to kilograms, multiply by 0.4542 To convert pounds (force) per square inch to kilopascals, multiply by 6.89

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Figure 1. Positive phase airblast parameters for a spherical TNT detonation in free-air at sealevel (U.S. Departments of the Army, Navy, and Air Force 1990).

For the normally reflected parameters, the structural element would be perpendicular to thedirection of the shock wave for Figure 4 to apply. Otherwise, the wave will strike the structure atan oblique angle.

When a plane wave strikes a structure at an angle of incidence, the oblique reflected pressureswill be a function of the shock strength. Although incident blast wave properties usually provideupper limits to blast loads on structures, the more usual case of loading of large, flat surfaces isrepresented by waves that strike at oblique incidence. Also, as a blast wave from a source somedistance from the ground reflects from the ground, the angle of incidence must change fromnormal to oblique.

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Figure 2. Positive phase airblast parameters for a hespherical TNT detonation in free-air atsea level (U.S. Departments of the Army, Navy, and Air Force 1990).

Confined Explosions

Confined and contained explosions that occur within structures normally develop complicatedpressure-time histories on the inside surfaces. Such loading cannot be predicted exactly, butapproximations and model relationships exist to define blast loads with a good confidence.These include procedures for determination of blast loads due to initial and reflected shocks,quasi-static pressure, directional and uniform venting effects, and vent closure effects. Theloading from a high-explosive detonation within a confined (vented) or contained (unvented)structure consists of two almost distinct phases. The first phase is the reflected blast loading,

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Figure 3. Reflected pressure as a function of angle of incidence (U.S. Department of theArmy, Navy, and Air Force, 1990)

Figure 4. Reflected impulse as a function of angle of incidence (U.S. Department of theArmy, Navy, and Air Force, 1990)

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which typically consists of an initial high-pressure, short-duration, reflected wave plus severallater reflected pulses. The second is called the gas loading phase.

Shock Pressure

Incident and reflected shocks inside structures consist of the initial high-pressure, short-durationreflected wave, plus several later reflected shocks which are a result of reverberation of the initialshock within the structure. These later pulses are usually attenuated in amplitude because of anirreversible thermodynamic process. These are complicated in wave forms because of theinvolved reflection process within the structure, whether vented or unvented. The simplest caseof blast wave reflection is that of normal reflection of a plane shock wave from a plane, rigidsurface. In this case, the incident wave moves at velocity U through still air at ambientconditions. The conditions immediately behind the shock front are those for the free-air shockwave. When the incident shock wave strikes the plane, rigid surface, it is reflected and movesaway from the surface with a velocity Ur into the flow field and compressed region associatedwith the incident wave. In the reflection process, the incident particle velocity us is arrested (us =0 at the reflecting surface), and the pressure, density, and temperature of the reflected wave areall increased above the values in the incident wave. The overpressure at the wall surface istermed the normally reflected overpressure and is designated Pr.

Following the initial internal blast loading, the shock waves reflected inward will usuallystrengthen as they implode toward the center of the structure, and then attenuate as they movethrough the air and re-reflect to load the structure again. The second shocks will usually besomewhat less in strength than the initial pulse, and after several such reflections, the shockwave phase of the loading will be over.

SHOCK (NCEL, 1988) is a computer code for estimating internal shock loads. This code can beused to calculate the blast impulse and pressure on all or part of a cubicle surface which isbounded by one to four rigid reflecting surfaces. The code calculates the maximum averagepressure on the blast surface from the incident and each reflected wave and the total averageimpulse from the sum of all the waves. The duration of this impulse is also calculated byassuming a linear decay from the peak pressure. This code based on the procedures in TM 5-1300 (U.S. Departments of the Army, Navy, and Air Force 1990). Shock impulse and pressureare calculated for each grid point for the incident wave and for the shock reflecting off eachadjacent surface. The program includes a reduced area option which allows determination ofaverage shock impulse over a portion of the blast surface or at a single point on the surface. Thecode calculates blast parameters for scaled standoff distances (R/W1/3) between 0.2 (0.079m/kg1/3) and 100.0 ft/lb1/3 (39.7 m/kg1/3). The program does not account for gas pressure loadcontributions. This is handled by using a separate method (i.e., the FRANG code) to predict thequasi-static portion of the load history and combining the two curves to form the completepressure-time history. It is important to note that the shock and quasi-static pressures are notadded where they overlap, but are merely intersected to define the load history.

The BLASTX code (Britt 1992), treats the combined shock wave (including multiple reflectionsoff walls) and explosive gas pressure produced by the detonation of a conventional high

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explosive in a closed or vented, rigid or responding (walls are allowed to fail under gas pressureloading), rectangular, cylindrical, or L-shaped rooms. The code allows the propagation ofshocks and gas into adjacent rectangular or box-shaped spaces. The shock wave effects can becalculated only for bare, spherical TNT explosive charges; however, the gas pressure model cantreat an arbitrary mixture of several explosive components. The code does have the capability totreat multiple non simultaneous explosions in a room, modifications of shock arrival times andpeak pressures to account for Mach stem effects, and the option to obtain pressure and impulsewave forms averaged over a number of target points on a wall. As with SHOCK, it does notaccount for movement of any of the walls or the roof, although recent versions of the code doallow openings to occur based on defined failure criteria and as created by combined shock andgas pressures. Gas pressures are propagated through failed surfaces. Shocks are not ventedthrough failed openings, however.

Another code is BLASTINW, a forerunner to BLASTX, is described in the literature (U.S.Department of Energy 1992). Initial shock loads are predicted using free-field curve fits to blastdata (Kingery and Bulmash 1984) and are converted to wall shock loads using results fromhydrocode calculations (Hikida and Needham 1981, Needham 1983). This shock wavereflection model is in good agreement with the standard TNT pressure and impulse peak valuesfor reflection at normal incidence over the pressure range from 1 to 90,000 psi (7 to 621 MPa).The code has been validated for selected cases for pressure up to about 1,000 psi (7 MPa) atoblique reflection angles. Effects of wall reflections are accounted for by postulating thedetonation of image charges behind each wall, with proper timing. Wave forms for the loads areobtained by fits to modified exponential decays for positive phases, and exponential times sinefunctions for negative phases. The code purports to properly handle Mach reflections, and itdoes account for loads from multiple shock reflections for all walls in the assumed closed room.The gas pressure model has been validated up to high pressure levels for TNT and PETN and tolower levels for other explosives (Britt 1989).

Gas Pressure

When an explosion from a high-explosive source occurs within a structure, the blast wavereflects from the inner surfaces of the structure, implodes toward the center, and re-reflects oneor more times. The amplitude of the re-reflected waves usually decays with each reflection, andeventually the pressure settles to what is termed the gas pressure loading realm. Whenconsidering poorly vented or unvented chambers, the gas load duration can be much longer thanthe response time of the structure, appearing nearly static over the time to maximum response.Under this condition, the gas load is often referred to as a quasi-static load. When consideringvented chambers, the gas pressure drops quickly in time as a function of room volume, vent area,mass of vent panels, and energy release of the explosion, and depending on the response time ofstructural elements under consideration, may not be considered quasi-static.

The gas load starts at time zero and overlaps the shock load phase without adding to the shockload, as illustrated in Figure 5, where the shock phase and the gas phase are idealized as such asthat shown and which should be used in design. They intersect at the load time pair (Pi, Ti) to

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p

Figure 5. Typical combined shock and gas load (U.S. Department of the Army, Navy, andAir Force, 1990)

form the bilinear load history, such as that shown and that should be used in design. Since theshock and gas loading are parts of the entire load history, although they are calculated separately,they should not be considered separately in design or analysis Various procedures are availablefor predicting the peak gas pressure in a structure (e.g., ConWep, Hyde 1993). One such curve isprovided in TM 5-1300 (U.S. Departments of the Army, Navy, and Air Force 1990), as shown inFigure 6. The charge weight to free volume ratio has to be computed, as described in TM 5-1300(U.S. Departments of the Army, Navy, and Air Force 1990).

Figure 6. Peak gas pressure for TNT detonation in unvented chambers (U.S. Department ofthe Army, Navy, and Air Force, 1990)

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Alternatively, the computer code FRANG (Wager and Connett 1989) can be used to calculate atime history of gas pressure and impulse which results from an explosion inside a rectangularroom. The code considers the effect of the escape of gas from the room through vents, bothuncovered and covered by a frangible panel. The vent area is a function of the frangible paneldisplacement with time while the uncovered vents have a constant vent area. The required inputfor the code includes charge weight and type, room volume, covered and uncovered vent areas,covered vent perimeter, unit surface weight of frangible panel, initial recessed depth of the panel,shock impulse on the panel, and the analysis time step.

Ballistic Attack

Another class of threats is related to ballistic attack. Information on various weapon systems thatcould be used for such applications can be found in several sources (e.g., Department of theArmy 1986, Conrath at al. 1999), and the following summary is based on information fromthose references. Ballistic threats are specified in terms of a projectile's caliber, its impactvelocity, its impact kinetic energy, and the number of such impacts to be expected or tested.Such threats are divided into the categories of ?small arms? (which is taken to include projectilecalibers up to, but not including, 12.7 mm or .50 caliber) and ?larger caliber? (which includesprojectiles of 12.7 mm or greater). A standard establishes four ballistic levels, as described inTable 2. Tests for the three small arms ratings consist of three shots near the center of thesample, while the test for the high-powered rifle consists of a single impact near the center of thesample. Nevertheless, there are other standards for such ordnance (e.g., The National Institute ofJustice, NIJ, or U.S. Department of State, Naval Civil Engineering Laboratory), as shown inTable 3 and Table 4.

All of the projectiles of Tables 2 through 4 are commercially available or are U.S. militaryrounds. Each of the specifications cited is intended to be used for the qualification of structuralcomponents designed to defeat the specified projectiles. The .50 and its 12.7 mm counterpart hasbeen widely distributed and adopted by almost all countries. Ammunition has been manufacturedin many countries, and it has bullet weight between about 500 and 700 grains, and muzzlevelocities between about 2800 and 3500 fps. All these rounds represent projectiles that may beencountered during a ballistic attack, and one can compute their penetration into variousmaterials by using procedures in various manuals (e.g., Department of the Army 1986), or withthe computer code ConWep (Hyde 1993).

Ground Shock

Usually, ground shock is not a significant issue for terrorist incidents, since such attacks involveabove ground explosions. Nevertheless, one may have to consider ground shock for special cases(e.g., if a threat might include a buried charge). This paper will not address this issue beyondproviding a reference to other sources that contain such information (e.g., ASCE 1985,Department of the Army 1986). Also, one could use ConWep (Hyde 1993) for assessing sucheffects.

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Table 2. Ratings of bullet-resisting material per UL-752

Power Rating Weapon Projectile/Weight(grains)/Type

Muzzle Velocity(fps )1

Kinetic Energy(ft-lb)

Medium-SmallArms

Super 38Automatic

130/Metal Case 1,230 457

High-SmallArms

.357 MagnumRevolver

158/Lead 1,450 740

Super-SmallArms

.44 MagnumRevolver

240/Lead 1,470 1,150

High-Rifle 30-06 Rifle 220/Soft Point 2,410 2,830

1 To convert feet to meters, multiply by 0.3048 2 To convert foot-pounds (force) to joules, multiply by 1.356

Fragmentation Effects

Fragmentation effects are expected to be associated with explosions and terrorist attacks. Theseeffects are complicated, but they can be assessed by using the procedures in several manuals(e.g., Department of the Army 1986, Department of the Army, Navy and Air Force 1990, USDepartment of Energy 1992, etc.). The procedures in these manuals enable one to estimate thepenetration of explosively driven fragments into various typical construction materials. Thesefragments could be from either military munitions or from improvised devices. Since theseprocedures are empirical and require the use of various tables and charts, it is more useful toemploy the computer code ConWep (Hyde 1993) for quick assessments. The combined effects offragments and blast is even more complicated, and the available practical approaches forassessing such effects are limited.

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Table 3. Threat level ratings per NIJ 0108.01

Armor Type Ammunition BulletWeight(grains)

NominalBullet

Velocity (fps)

Nominal KineticEnergy (ft-lb)(E = 0.5mv2)

I 22 LRHV Lead38 Special RN Lead

40158

1,050850

100255

II-A 357 Magnum JSP9-mm FMJ

158124

1,2501,090

550330

II 357 Magnum JSP9-mm FMJ

158124

1,3951,175

685380

III-A 44 Magnum LeadSWC Gas Checked

99-mm FMJ

240

124

1,400

1,400

1,050

540

III 7.62-mm M80 FMJ(308 Winchester)

150 2,750 2,520

IV Cal .30 AP M2 166 2,850 3,000

Table 4. Ballistic ratings per SD-STD-01.02

Ballistic Rating Cartridge NominalVelocity

(fps)

Kinetic Energy(ft-lb)

(E = 0.5mv2)

Minimum StandardSubmachine Gun12-Gauge Shotgun

9-mm, 115-grain FMJ (Steel Jacket)#4 Buck Shot

1,4001,325

500NA

Rifle StandardRifle

12-Gauge Shotgun

7.62-mm NATO, M80 Ball 147 grains5.56-mm, M193, Ball 55 grains#4 Buck Shot

2,7503,1851,325

2,4701,240NA

Rifle Standard (AP)Rifle, AP

12 Gauge Shotgun

7.62-mm AP, M61, 150-grain30-06, AP, M2, 165-grain#4 Buck Shot

2,7502,8501,325

2,5202,980NA

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Conclusions and Recommendations

Defending society against terrorism requires a well planned layered approach. Besides theserious needs for innovative intelligence and law enforcement capabilities to counter suchthreats, society must invest in the development of effective protective technologies. Suchtechnologies, that are vital for insuring the safety of people and the preservation of valuableassets, are the last layer of defense against this type of incidents. The future of R&D in protectivetechnology must be reshaped accordingly. The study of heavily fortified military facilities mayno longer be the main area of concern (although the technology in this area must be keptrelevant).

Careful attention must be devoted to typical civilian facilities whose failure could severelydisrupt the social and economic infrastructure of nations. We lack essential knowledge on howsuch facilities (office buildings, schools, hospitals, power stations, etc.) behave under blast,shock, impact and fire loads. Many materials and components that are typically used in suchbuildings were never studied for these applications. Furthermore, one must not employ onlyempirical approaches to address these issues (e.g., using high explosive tests to observeconsequences).

One must employ innovative approaches that combine theoretical, numerical and experimentalapproaches, and to conduct these activities in a well-coordinated collaborative activity betweengovernment, academic, and private organizations. Furthermore, this development must beconducted in the context of “multi-protective technology”, addressing the complementary needsand potential benefits of addressing natural hazards and threats associated with human activities.This general field is one of the last frontiers in engineering that provides both tremendouschallenges and the potential for great achievements.

To address these issues, one must establish comprehensive long- and short-term R&D activitiesin protective technology, and to develop innovative and effective blast, shock, impact and firemitigation technologies. These are required to insure the safety of government, military andcivilian personnel and facilities under evolving terrorist threats. Furthermore, to launch effectivetechnology transfer and training vehicles that will insure that the required knowledge andprotective technologies will be fully and adequately implemented.

Since this evolving threat affects many countries and it endangers the stability of the entireworld, the required R&D should be conducted in a collaborative multinational framework.

References

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ASCE, Design of Structures to Resist Nuclear Weapons Effects, American Society of CivilEngineers, Manual No. 42, 1985.Baker, W.E., Explosions in Air, Wilfred Baker Engineering, San Antonio, 2nd Printing, 1983.

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Baker, W.E., Cox, P.A., Westine, P.S., Kulesz, J.J., Strehlow, R.A., Explosion Hazards andEvaluation, Elsevier, 1983.

Britt, J.R., Enhancements of the BLASTX Code for Blast and Thermal Propagation in ProtectiveStructures: BLASTX Version 2.0, prepared for U.S. Army Engineer Waterways ExperimentStation, Vicksburg, MS, by Science Applications International Corporation, November 2, 1992.

Conrath, E.,J., Krauthammer, T., Marchand, K.A., and Mlakar, P.F., Structural Design forPhysical Security, ASCE, 1999.

Cranz, C., Lehrbuch der Ballistik, Springer-Verlag, Berlin, 1926.

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Hokanson, J.C., Esparza, E.D., Wenzel, A.B. and Price, P.D., Blast Effects of SimultaneousMultiple-Charge Detonations, Contractor Report ARLCD-CR-78032 (AD-E400 232),U.S. Army ARRADCOM, Dover, NJ, October 1978.

Hopkinson, B., British Ordnance Board Minutes, 13565, 1915.

Huffington, N.J., Jr., and Ewing, W.O., Reflected Impulse Near Spherical Charges, TechnicalReport BRL-TR-2678, U.S. Army BRL, Aberdeen Proving Ground, MD, September 1985.

Hyde, D.W., User Guide for Microcomputer Code ConWep, Instruction Report SL-88-1, USArmy, Waterways Experiment Station, April 1988 (Revised 22 February 1993).

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